Castletown is a town in the Isle of Man, geographically within the historical parish of Malew but administered separately. Lying at the south of the island, it was the Manx capital until 1869. The centre of town is dominated by Castle Rushen, a well-preserved medieval castle, originally built for a Viking king.

The Isle of Man or Mann, is a self-governing British Crown Dependency in the Irish Sea, between Great Britain and Ireland. It is recognized as one of the Celtic nations, and is the homeland of the Manx people, a Celtic ethnic group. As head of state, Charles III holds the title Lord of Mann and is represented by a Lieutenant Governor. The government of the United Kingdom is responsible for the isle's military defence and represents it abroad.